The present invention relates to disc drive storage systems and, more particularly, to a head suspension assembly having a flexure displacement limiter.
Disc drives of the "Winchester" type are well known in the industry. Such drives use rigid discs coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor which causes the discs to spin and the surfaces of the discs to pass under respective recording heads. A recording head includes a hydrodynamic (e.g. air) bearing slider and a transducer for writing information to and reading information from the disc surface. An actuator mechanism moves the heads from track to track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a head suspension assembly for each head.
The head suspension assembly includes a load beam and a gimbal. The load beam provides a preload force which forces the head toward the disc surface. The gimbal is positioned between the load beam and the slider to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc. The slider includes an air bearing surface which faces the disc surface. A conventional catamaran slider includes a pair of raised side rails which face the disc surface and form air bearing surfaces. As the disc rotates, the disc drags air under the slider along the air bearing surfaces in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the side rails, skin friction on the air bearing surfaces causes the air pressure between the disc and the air bearing surfaces to increase which creates a hydrodynamic lifting force that causes the slider to lift and fly above the disc surface. The preload force supplied by the load beam counteracts the hydrodynamic lifting force. The preload force and the hydrodynamic lifting force reach an equilibrium based upon the hydrodynamic properties of the slider and the speed of rotation of the disc.
The preload force is transferred from the load beam to the back surface of the slider through a spherical load point button, which is typically a stamped feature on the gimbal having an apex that contacts the under surface of the load beam. The load point button provides a point about which the slider can pitch and roll and limits vertical displacement of the head and gimbal in a direction away from the disc surface. However, this structure does not limit vertical displacement in a direction toward the disc surface, which can cause damage to the delicate flexure features of the gimbal.
Undesirable vertical displacement can occur due to forces applied during assembly, fly testing or shipping and handling. For example, transportation shock may generate displacement forces large enough to yield the twisted wire electrical interconnections to the head or cause the delicate flexure features of the gimbal to bend past their yield point, which may result in separation between the load beam and the head at the load point button. Also, certain disc drives have a ramp which lifts the load beam to unload the slider from the disc surface during start and stop of disc rotation. If the slider is a self-loading slider, subambient pressure developed between the slider and the disc surface can cause a large vertical displacement of the gimbal as the slider is lifted from the disc surface. This displacement can cause damage to the gimbal flexure features.
One attempt at solving this problem is to form "hooks" on the gimbal which wrap around the distal end of the load beam to prevent the undesirable vertical motion. The primary disadvantage of this approach is that during assembly, the gimbal must be slid in a longitudinal direction along the load beam to interleave the gimbal between the load beam and the formed hooks. Once interleaved, the gimbal can be aligned for welding to the load beam. This results in a suspension assembly that is very difficult and time consuming to manufacture.